SU8045A1 - Device for the automatic regulation of the power factor of a synchronous motor - Google Patents

Description

As is well known, in a conventional synchronous motor, the power factor (cos tp) varies with the load. In order for cos tp of such an engine to remain approximately constant at all loads, it is necessary to change the excitation current I accordingly, increasing it with increasing load and decreasing with decreasing load on the motor shaft.

It is possible to obtain the full automaticity of adjusting the excitation current 7, кор if used as an exciter, instead of the commonly used DC dynamo, one root converter with subtly expressed poles (with the same air gap around the entire circumference like an asynchronous motor).

In FIG. 1 shows a diagram of an apparatus for automatically adjusting the power factor of a synchronous motor; FIG. 2-change of the angle of inclination of the flow axis of the drive driver with respect to the axis of the brushes to change the load of the main engine; FIG. 3 — modification of the circuit of the device shown in FIG. 1, characterized in that the contact rings of the drive inverter are not fed directly from the three-phase network, but through the stator winding of the main motor; FIG. 4-modification of the device of FIG. 1, characterized in that the winding of the inverter core is connected to the network via a booster transformer.

The three-phase line LL (Fig. 1) involves the stator winding S of the main motor, the rotor of which JR is equipped with slip rings K-KK, and the rotor winding AND exciter, similar to the winding of the rotor asynchronous motor equipped with slip rings KI and having same

the number of poles as the main engine. In addition to winding K, an exciter is located on the exciter rotor, a coil of direct current –Bg with a “collector and brushes BB. The wires of the winding 2 can be located in the same grooves as the BI-winding wires, or in separate ones; The windings RI and I can also be combined into one common. The rotor sits on the same shaft with the rotor of the main motor I. The stator winding of the S-exciter, evenly distributed in the slots like the asynchronous motor stator, should have the number of poles, as well as the windings of the i and E, the same as the number of poles of the main engine.

At a synchronous rotational speed, the exciter operates as one sequential excitation transducer, receiving three-phase current from the network L through the contact rings-K i. In this case, a DC voltage appears on the driver's collector. As can be seen from FIG. 1, the direct current of the driver 1, emerging from the positive u & B, flows around the rotor winding S of the main motor, flows along the stator winding j of the driver and hits the negative brush B, on the collector of the driver. The excitation current 1, when the load on the main motor shaft changes, will also change its value, and the nature of the change in current j will depend on the magnitude of the displacement angle of brushes BB on the exciter collector. The main synchronous motor will operate with a high power factor close to one, despite the change in the load on the shaft of this motor; The reason for this is that the exciter current (s) that feeds the rotor winding of the main motor will automatically increase with increasing load.

The operation of the device is as follows. During the synchronous rotation of the unit, the rotating magnetic field F, created jointly by the rotor winding BI and the stator winding of the S converter, is stationary in space relative to the stator S. The DC coil E of the exciter rotates in this magnetic field F, as a result of which a DC voltage E appears on the collector between the brushes B-B (Fig. 2j, the value of which depends on the position of the flow axis F relative to the brushes axis. With a change the load of the main motor, the angular displacement of the rotor B of the main motor relative to the axis of rotating stresses of the stator S. In accordance with this, the angle of inclination of the flow axis F relative to the axis of the brushes -5-B (Fig. 2) also changes, i.e. when changing the load of the main engine and also varies.

It is possible to find such a position of the brushes on the collector of the exciter core -Y2, in which with an increase in engine load an increase in angle a will occur thus in fig. 2 angle “i will correspond to small loads, and angle to large loads. So, with increasing load, the voltage of the driver E will increase, and in connection with this, the constant excitation current I flowing in the rotor L of the main motor will also increase.

The diagram of FIG. 1 can be modified as shown in FIG. 3. The latter scheme is characterized in that the RI contact rings of the converter driver are fed not directly from the three-phase network L, but through the stator winding S of the main motor. For this purpose, all three ends of this Sue stator winding are connected to the zero point, as usual, but connected to contact rings KI of the exciter. Due to such a connection, the current 1, before getting into measles RI of the exciter, passes the preliminary winding of the stator 8, where almost all the mains voltage is lost;

therefore, on the rings K we will have a comparatively small voltage EI, equal to the voltage of the network P minus the voltage D lost in the stator winding S: E, P – E.

With such a circuit, there is no need for a transformer that reduces the voltage across the j-rings. The second advantage of the circuit of FIG. 3 is the following. With increasing load, a corresponding decrease in e occurs. The force E induced in the stator winding 8, as a result of which the voltage E P - E on the exciter rings KI increases, which in turn entails an increase in the DC excitation current 1 feeding the rotor R of the main motor.

A change in the excitation current / with a change in load can be intensified to an even greater degree if the feed rings K of the exciter from the network X are energized by switching on the booster transformer T (Fig. 4). Such a circuit can be used in the case of a synchronous capacitor, with the aim of improving the cos f transmission line.

FIG. Figure 4 shows such a synchronous capacitor-S-D whose rotor is powered by direct current 1 from driver R. In FIG. 4 means: G generator station; L-line transmission; M-receiving station.

The secondary winding of the transformer Y must be turned on in such a way that with increasing current Z. in the line L, the voltage E- increases on the KI converter rings.

FIG. 1 and 3, the rheostat g serves to limit the amount of current in the driver circuit at the first moment after turning on the rotor winding R of the main motor to the driver's collector. The rheostat g can also be used to start up the main engine in xB, turning it on

as shown in FIG. 3. As can be seen from this figure, a starting rheostat r connected in series with the three phases of the stator winding Oj.-81-Si exciter is connected to the winding circuit of the rotor R of the main engine during the popping. Due to this, during start-up, the current in the rotor R of the main motor is limited and the start-up impetus of the current is thus softened. After the end of the run, the resistance r can be deduced.

All described nd FIG. I-4 schemes have the peculiarity that with these schemes the main engine automatically goes into synchronization.

The subject of the patent.

1. A device for automatic regulation of the power factor of a synchronous motor, characterized in that it consists of an exciter that is mounted on a cfiHxpoHHoro S-R motor and has a three-phase winding / Si on the stator and two on the core

windings, a conventional three-phase winding -B-B and a conventional collector winding B equipped with a collector, the first winding R connecting to the network supplying the synchronous motor, and the second winding R connecting the common closed circuit to the rotor winding R synchronous motor and with the stator winding of the exciter S (Fig. 1).

2. The modification of the device described in paragraph 1, characterized in that the winding RI of the driver core is connected in series with the winding 8 of the synchronous motor stator (Fig. 3).

3. Variation of the device described in section 1, characterized in that the winding R of the converter core is connected to the network via the booster transformer T, (FIG. 4).